Renewable (self-sustaining) energy is one of the most read about and discussed topics in the world. It encompasses many different alternative energy sources, e.g., solar, wind, hydro, tidal, nuclear, biomass, geothermal and, more recently, kinetic energy produced from moving cars. Renewable energy sources, when compared to conventional fossil fuel energy sources such as oil, coal and gas, have substantial advantages. Yet, they can be difficult and often expensive to harness, and a large amount of such an energy source is typically needed to produce only a small amount of useful electrical or fuel energy. The generation and utilization of renewable energy often poses environmental challenges, requires new infrastructure and enormous investments before generating revenue. As a result, the alternative energy industry has been slow to develop, despite government spending, regulations and policies to support its growth.
In contrast, oil, coal and gas are efficient energy sources and small amounts can produce or be used to produce relatively large amounts of electrical or fuel energy. Fossil fuel energy has a massive established base and continues to comprise the easiest and least expensive obtainable energy source. As a result, fossil fuels will likely remain the world's predominant sources of energy for the next several decades. Climate change concerns, high price swings in the cost of oil and increasing government support, however, will continue to drive renewable energy legislation, incentives and commercialization despite the problems each face with technology, public acceptance and economic viability. More importantly, there remains an opportunity to develop a broader mix of practical and economical renewable energy sources if future global needs are to be met.
In the United States alone, traffic flow along the nation's roads represents a significant, stable source of kinetic energy associated with such motion. The U.S. Energy Information Administration (EIA) reports that there are 55,650,943 paved roads in the United States totaling nearly 3.9 million miles of roadway. The total U.S. vehicle stock comprises some 255 million registered vehicles, with residential vehicles accounting for 83% of the total. Nonresidential vehicles, comprising business fleets and government operated vehicles (federal, state, county, and municipal governments) account for 17% of the total. According to the latest available annual survey, U.S. residential vehicles traveled 1,793 billion miles. In terms of total traffic, the average mile of roadway was traversed by residential and non-residential vehicles 1,557 times per day. On high traffic toll and non-toll roads, including highways and interstate segments, there substantially more total traffic per mile of roadway—between 45,000 and 65,000 vehicles on an average day. The harnessing of even a miniscule portion of the energy from such traffic flow, particularly in these high traffic areas, could position this energy source to compete with other forms of alternative energy such as wind and solar by reducing the variability.